package com.kevin.list;

import com.kevin.list.AbstractList;
import com.kevin.list.List;

import java.util.Objects;

/**
 * @Author LXL
 * @Date 2020/9/22 16:41
 **/
public class ArrayList<E> extends AbstractList<E> implements List<E>{

    private E[] elements;

    private static final int DEFAULT_CAPATICY = 10;

    public ArrayList(int capaticy){
        capaticy = capaticy < 0 ? DEFAULT_CAPATICY : capaticy;
        elements = (E[]) new Object[capaticy];
    }

    public ArrayList(){
        this(DEFAULT_CAPATICY);
    }

    /**
     * 清除所有元素
     */
    @Override
    public void clear() {
        for (int i = 0 ; i < size ; i++){
            elements[i] = null ;
        }
        this.size = 0;
    }

    /**
     * 获取index位置的元素
     * @param index
     * @return
     */
    @Override
    public E get(int index) {
        rangeCheck(index);

        return elements[index];
    }

    /**
     * 设置index位置的元素
     * @param index
     * @param element
     * @return 原来的元素ֵ
     */
    @Override
    public E set(int index, E element) {
        rangeCheck(index);

        E old = elements[index];
        elements[index] = element;
        return old;
    }

    /**
     * 在index位置插入一个元素
     * @param index
     * @param element
     */
    @Override
    public void add(int index, E element) {
        rangeCheckForAdd(index);

        ensureCapacity(size + 1);
        for (int i = size ; i > index; i--){
            elements[i] = elements[i - 1];
        }
        elements[index] = element;
        size++;
    }

    /**
     * 删除index位置的元素
     * @param index
     * @return
     */
    @Override
    public E remove(int index) {
        rangeCheck(index);

        E old = elements[index];
        for (int i = index + 1; i < size; i++){
            elements[i - 1] = elements[i];
        }
        elements[--size] = null;
        return old;

    }

    /**
     * 查看元素的索引
     * @param element
     * @return
     */
    @Override
    public int indexOf(E element) {
        if (element == null){
            for (int i = 0 ; i < size ; i++){
                if (elements[i] == null){
                    return i;
                }
            }
        }else {
            for (int i = 0 ; i < size ; i++){
                if (element.equals(elements[i])){
                    return i;
                }
            }
        }
        return ELEMENT_NOT_FOUND;
    }

    /**
     * 保证要有capacity的容量
     * @param capacity
     */
    private void ensureCapacity(int capacity) {
        int oldCapacity = elements.length;
        if (oldCapacity >= capacity) {
            return;
        }
        int newCapacity = oldCapacity + (oldCapacity >> 1);
        E[] newElements = (E[])new Object[newCapacity];
        for (int i = 0 ; i < size ; i++){
            newElements[i] = elements[i];
        }
        elements = newElements;
        System.out.println(oldCapacity + "扩容为" + newCapacity);
    }

    @Override
    public String toString() {
        StringBuilder string = new StringBuilder();
        string.append("size=").append(size).append(", [");
        for (int i = 0; i < size ; i ++){
            string.append(elements[i]);
            if (i != size - 1) {
				string.append(", ");
			}
        }
        string.append("]");
        return string.toString();
    }
}
